1. Field of the Invention
The field of the invention relates to control and injection lines for use in the oil and gas industry. When used as a control line the invention has application to the operation of subsurface valves used in oil or gas producing well bores. Such lines also find application to downhole chemical injection systems for corrosion protection. The lines also find application for use as blowout preventer control lines, instrument package deployment cables, etc.
2. Description of the Prior Art
U.S. Pat. No. 3,844,345, issued in the names of Evans and Newman, discloses encapsulated control tubes in a sheath of elastomeric material so that the encapsulated control lines may be easily handled and fit against production tubing. The encapsulated control line of U.S. Pat. No. 3,844,345 is designed specifically to control subsurface control valves via the fluid control tubes in the encapsulated control lines. Its shape is such that a surface blowout preventer may advantageously completely seal the annular space about the production tubing and the control line fit against it.
U.S. Pat. No. 4,262,703 issued in the names of Moore and Kendall shows a control line for attachment to an underwater oil or gas flow line for attachment to a downhole tubing string or for control in subsea workover operations. The control line of this patent includes two tension-bearing members such as wire ropes and includes hydraulic tubes and electrical and electronic lines encapsulated in a resilient elongated body.
Similar kinds of encapsulated control lines are used for injecting corrosion inhibiters in downhole chemical injection systems. For this application, one or more wire ropes are provided which extend generally along one or more control lines. The control lines and wire ropes are encapsulated in an elastomeric sheath in the same fashion as are those of U.S. Pat. No. 3,844,345.
As indicated above, the encapsulated control or flow lines of U.S. Pat. No. 3,844,345 are especially adapted to be secured to production tubing which extends through a surface disposed blowout preventer during that phase of completing an oil or gas well of positioning the production tubing in the well. After the tubing is secured in place in the well, the blowout preventer is removed and a production "Christmas tree" is placed at the surface of the well to safely control high pressure gas or oil flowing from the well.
During the time that the tubing and the attached flow lines extend through the blowout preventer, high pressure conditions in the well are controlled by closing the blowout preventer, thereby closing the vertical flow path of the well which surrounds the tubing and flow lines. Since the strength or anti-crushing member of the control or flow line may be open to pressurized fluid or gas in the well, there has existed the possibility that high pressure fluid or gas could migrate to the surface past the blowout preventer via the voids or interstices in the strength or anti-crushing member in the flow line, even though the blowout preventer completely seals the vertical flow path about the outside of the production tubing and attached control or flow line.